1. Field of the Invention
The present invention relates to thermoelectric modules and processes for producing the same. More particularly, the invention relates to a thermoelectric module using a small amount of material per unit output thereof, and a process for producing thermoelectric modules of the kind described above with a high yield and a low processing cost.
2. Description of the Prior Art
Conventional thermoelectric modules are produce by a process comprising cutting a melt-grown ingot of thermoelectric material into bulk thermoelectric elements and bonding electrodes to the thermoelectric elements through soldering or the like. According to an alternative process, a chalcogenide alloy powder is vacuum-sealed or sealed with inert gas in an ampule and sintered to produce thermoelectric elements. Thermoelectric elements which are formed in these processes have a high figure of merit and provide the advantage of giving good thermoelectric conversion characteristics to thermoelectric modules.
However, the conventional production of thermoelectric modules in which use is made of an ingot of thermoelectric material involves the following serious problems:
(1) since the yield of thermoelectric elements notably decreases when the thickness thereof is reduced to 1.5 mm or less, miniaturization of thermoelectric elements is difficult, with the result that the amount of a thermoelectric material used is inevitably large per unit output of a thermoelectric module and the material cost is high;
(2) because of cracking of the thermoelectric material in the cutting step and a high probability that electric conduction will be poor or that a short circuit will occur across electrodes because of electrodes that fail to bond to the thermoelectric elements through soldering or the like technique, the yield is notably lowered through the process of production of thermoelectric nodules with a high probability that defective nodules will be formed; and
(3) since thermoelectric elements not only are produced one by one but also are brittle, automation of the production process is difficult and hence the processing cost is high.
The alternative process, in which use is made of sintering of a chalcogenide alloy powder, has the problem of low productivity because pressure molding is necessary and moldings must be sintered while being sealed in a container such as an ampule. And by this alternative process, thermoelectric elements are produced one by one in the same manner as the conventional process, so that automation of the production process and reduction of processing cost are difficult.